Device and method for desalinating salt water and method of producing carbon dioxide exhausting means

ABSTRACT

A salt water desalinating device, characterized by having an absorption refrigerating machine using a first dilute salt water and concentrated salt water and characterized in that a second dilute salt water to be desalinated is evaporated by heat flowing out from the high-temperature heat source of the absorption refrigerating machine and vapor evaporated from the second dilute salt water is condensed by heat to be absorbed to a refrigeration source. A plurality of the absorption refrigerating machines may be series-connected in a series arrangement. A method of desalinating salt water comprising the steps of supplying a first dilute salt water to a refrigeration source, supplying concentrated salt water to a high-temperature heat source, discharging the first dilute salt water having a high concentration after water evaporation, discharging the concentrated salt having a low concentration after water absorption, discharging the second dilute salt water having a high concentration after water evaporation and recovering condensed fresh water.

TECHNICAL FIELD

The present invention relates to a desalinating apparatus using anabsorption refrigerator which utilizes natural energy, a desalinationsystem, a method of desalinating saline water, and a method of producingright of emitting carbon dioxide, and more particularly relates to adesalinating apparatus using an absorption refrigerator ofopen-regeneration type which utilizes dilute saline water andconcentrated saline water, a desalination system, a desalinating method,and a method of producing right of emitting carbon dioxide.

BACKGROUND ART

In an arid region, a region where soil is deteriorated with salt, or aregion where severe contamination of water takes place, supply of freshwater is an important issue, which can be utilized for household use,industrial use, agricultural use, improvement of soil properties,prevention of salt-precipitation in soil, or the like. In addition,regulation over carbon dioxide emission into the atmosphere with theconsumption of fossil fuel is focused on in recent years, in connectionwith issues on the global greenhouse effect. Therefore, a transaction ofa right of emitting carbon dioxide is also under consideration. In thiscontext of the global greenhouse effect, there are attempts for removingcarbon dioxide from the atmosphere through regeneration (recover) ofvegetation in arid regions. When fresh water produced by a desalinationprocess is utilized for this purpose, the subject is how to desalinatesaline water using natural energy.

As background arts for desalinating saline water such as seawater, thereare a multi-stage flash distillation method, a multi-effect distillationmethod, a reverse-osmosis method, an electrodialysis method, a vaporcompression method, a freezing method, and so on. Even when thereverse-osmosis method is employed, which is considered to consumesmaller amount of energy in desalinating seawater, electricity of 7kWhis practically consumed in producing 1 ton of fresh water. Therefore, apractice of such desalination is actually accompanied by a large amountof fossil fuel-consumption, which gives rise to problems from a point ofview of costs, saving energy, reducing carbon dioxide emission, and soon.

Desalination which utilizes solar energy and which does not consumefossil fuel has been widely tried. For example, a system which producesfresh water by a reverse osmosis method utilizing electricity generatedby a solar thermal generator or solar batteries and another system whichproduces fresh water by a distillation method which utilizesdifferential temperature of seawater or solar thermal energy have beenstudied. However, there are problems in costs. Although throughput of amulti-effect distillation method which utilizes solar thermal energy isof several 10 kg/day per unit area (1 square meter) of solar radiation,which is relatively large, the problem is that the costs of obtaining adurable structure against natural conditions such as a strong wind or anadhesion of sands are remarkably increased.

As a kind of heat-pump which is employed in an air-conditioning andheating system, absorption refrigerators are widely spread, whichutilize thermal energy. As a heat source for these, solar thermal energyetc. other than the fossil fuel can be utilized. A type of absorptionrefrigerator having an open-regeneration field is known, which employs asolution of lithium bromide or calcium chloride and which utilizes solarthermal energy. This is a system suitable for arid regions. However,there are few studies on this absorption refrigerator for desalination.Furthermore, there are few studies on structure of a low-cost absorptionrefrigerator which is fit for desalination utilizing natural energy.

DISCLOSURE OF THE INVENTION

The present invention is made in view of the above-mentioned subjects,and an object of the present invention is to develop a novel fresh waterresource therefor. Another object of the present invention is to providea novel desalinating apparatus which utilizes natural energy. Yetanother object of the present invention is to provide a noveldesalination system which utilizes natural energy. Still another objectof the present invention is to provide a novel method of desalinatingsaline water which utilizes natural energy. Still another object of thepresent invention is to provide a novel method of producing right ofemitting carbon dioxide which contributes to control over atmosphericemission of carbon dioxide in desalinating saline water. Still anotherobject of the present invention is to provide a novel method ofproducing right of emitting carbon dioxide, which stimulates fixation ofcarbon dioxide of atmosphere by means of vegetation which are producedthrough desalinated saline water. Accordingly, the above-mentionedobjects and other related objects are achieved by the present inventiondisclosed herein.

Namely, a desalinating apparatus according to an embodiment of thepresent invention includes an absorption refrigerator which operatesusing concentrated saline water and first dilute saline water. Thefeatures are that second saline water for desalination is evaporatedutilizing heat which flows out from a high-temperature heat source ofthe absorption refrigerator, and that fresh water is obtained throughcondensation of water vapor which has been evaporated from the secondsaline water utilizing heat which flows in a refrigeration source of theabsorption refrigerator.

In the above desalinating apparatus, plural absorption refrigerators maybe employed, which may be disposed in series in a serial arrangement.

A desalinating apparatus according to another embodiment of the presentinvention includes a plurality of absorption refrigerator units, eachincludes a refrigeration source plate having no water-permeability, afirst dilute saline water holding member which is brought into closecontact with a surface of the refrigeration source plate, ahigh-temperature heat source plate having no water-permeability, aconcentrated saline water holding member which is brought into closecontact with a surface of the high-temperature heat source plate andwhich is disposed opposite the first dilute saline water holding member,and a second dilute saline water holding member which is brought intoclose contact with another surface of the high-temperature heat sourceplate. Further, the plurality of absorption refrigerator units arealigned in series in a serial arrangement, wherein each second dilutesaline water holding member is disposed opposite another surface of theadjacent refrigeration source plate.

In the above desalinating apparatus, each of the plurality of absorptionrefrigerator units may further include a fresh water holding memberwhich is brought into close contact with another surface of therefrigeration source plate.

In the above desalinating apparatus, a plurality of gap-keeping membersmay further be provided for keeping within a prescribed range a gapbetween the first dilute saline water holding member and theconcentrated saline water holding member and a gap between the seconddilute saline water holding member and the refrigeration source plate.

In the above desalinating apparatus, the serial arrangement may be madealong a closed line.

In the above desalinating apparatus, a vacuum system may further beprovided, which includes a vacuum chamber in which a space including theplurality of absorption refrigerator units is evacuated so as to havesubstantially the same pressure.

A desalination system according to yet another embodiment of the presentinvention includes means for supplying first dilute saline water, meansfor supplying concentrated saline water, means for supplying seconddilute saline water for desalination, an absorption refrigerator whichutilizes the concentrated saline water and the first dilute salinewater, means for evaporating the second dilute saline water, whichutilizes heat flowing out from the high-temperature heat source of theabsorption refrigerator, and means for collecting condensed fresh water,which condense the water vapor evaporated from the second dilute salinewater utilizing heat flowing in the refrigeration source of theabsorption refrigerator.

In the above desalination system, means for heating the concentratedsaline water and means for heating the dilute saline water may furtherbe provided. In this case, means for exchanging heat of water whichflows in the absorption refrigerator for that of water which flows outtherefrom.

In the above desalination system, a vacuum system which evacuates theabsorption refrigerator may further be provided.

In the above desalination system, a salt-precipitation field whichre-concentrate the concentrated saline water in which asalt-concentration thereof has been decreased.

A method of desalinating saline water using an absorption refrigeratoraccording to still another embodiment of the present invention includesthe steps of supplying first dilute saline water to a refrigerationsource of the absorption refrigerator, supplying concentrated salinewater in which molar salt-concentration thereof is higher than that ofthe first dilute saline water to a high-temperature heat source of theabsorption refrigerator, supplying second dilute saline water fordesalination to the absorption refrigerator, draining the first dilutesaline water in which salt-concentration thereof has been increased dueto evaporation of water, draining the concentrated saline water in whichsalt-concentration thereof has been decreased due to absorption ofwater, draining the second dilute saline water in whichsalt-concentration thereof has been increased due to evaporation ofwater, and collecting condensed fresh water. Features of the method ofdesalinating saline water are that the fresh water for desalination isproduced through evaporation of the second dilute saline water usingheat flowing out from the high-temperature heat source of the absorptionrefrigerator and through condensation of water vapor which hasevaporated from the second dilute saline water using heat absorbed inthe refrigeration source of the absorption refrigerator.

In the above desalinating method, the step of regenerating theconcentrated saline water which re-evaporates water of the concentratedsaline water in which concentration thereof has been decreased due toabsorption of water may further be provided.

In the above desalinating method, the step of evacuating the absorptionrefrigerator may further be provided.

In the above desalinating method, the step of heating the first dilutesaline water, the second dilute saline water, and the concentratedsaline water supplied. In this case, the step of exchanging heat of thefirst dilute saline water, the second dilute saline water, and theconcentrated saline water supplied for heat of the first dilute salinewater, the second dilute saline water, the concentrated saline waterexhausted, and the fresh water collected, may further be provided.

A method of producing right of emitting carbon dioxide is providedaccording to still another embodiment of the present invention. Thissubstitutes a desalination system which emits a high amount of carbondioxide to a desalination system which utilizes natural energy, andobtains a right of emitting carbon dioxide by operating the desalinationsystem which utilizes natural energy according to the above-mentionedmethod of desalinating saline water.

A method of producing right of emitting carbon dioxide according tostill another embodiment of the present invention may produce a right ofemitting carbon dioxide through the step of fixing carbon dioxide of theatmosphere, wherein vegetation is grown using the fresh water which isproduced as described above.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a conceptual view illustrating an outline of a desalinatingapparatus according to an embodiment of the present invention.

FIG. 2 is a conceptual view illustrating an outline of one unit of anabsorption refrigerator which is employed in the desalinating apparatusof FIG. 1.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to FIG. 1 and FIG. 2, preferred embodiments of the presentinvention are explained. However, any known structure may be employed asa structure of an absorption refrigerator which is employed in adesalinating apparatus of the present invention.

FIG. 1 illustrates an outline of an example according to an embodimentof the present invention. Further, FIG. 2 illustrates an outline of oneabsorption refrigerator unit which is employed in the embodiment of FIG.1.

The absorption refrigerator 10 illustrated in FIG. 2 includes ahigh-temperature heat source 11 having a high-temperature heat sourceplate 111 having no water-permeability and a refrigeration source 12having a refrigeration source plate 121 having no water-permeability.The high-temperature heat source plate 111 having no water-permeabilityand the refrigeration source plate 121 having no water-permeability aredisposed opposite each other. A concentrated saline water holding member112 is disposed so as to be brought into close contact with a surface ofthe high-temperature heat source plate 111. Further, a first dilutesaline water holding member 122 is disposed so as to be brought intoclose contact with a surface of the refrigeration source plate 121. Theconcentrated saline water holding member 112 and the first dilute salinewater holding member 122 are disposed opposite each other with aprescribed distance. Further, this absorption refrigerator alone canoperate as a desalinating apparatus.

In the example according to the embodiment as mentioned above, 6 unitsof absorption refrigerators 10, each has the structure illustrated inFIG. 2, are aligned in series in a serial arrangement, where the serialarrangement implies that the refrigeration source of one absorptionrefrigerator unit is thermally connected with the high-temperature heatsource of the adjacent absorption refrigerator unit. In FIG. 1, therefrigeration source 12 of one absorption refrigerator unit 10 isdisposed opposite the high-temperature heat source 11 of the adjacentabsorption refrigerator unit 10. The number of the absorptionrefrigerators is 6. However, any number thereof may be aligned.

Principle of operation of the desalination according to the presentinvention is briefly described as follows. Namely, a partial pressure ofsaturated water vapor which is in equilibrium with first dilute salinewater that is supplied to the first dilute saline water holding member122 is higher than a partial pressure of concentrated saline water whichis held by the concentrated saline water holding member 112 and whichhas a higher temperature than that of the first saline water. Therefore,water vapor which has evaporated from the first saline water having lowtemperature is absorbed in the opposite concentrated saline water whichhas the high temperature, through one-directional diffusion of watervapor. In this case, heat of the first dilute saline water having a lowtemperature is transferred to the concentrated saline water having ahigh temperature. This is a kind of heat-pump, and constitutes anabsorption refrigerator. The differential temperature obtained is largewhen the differential concentration of the saline water is large. Thehigh-temperature heat source is on the concentrated saline water, andthe refrigeration source is on the first saline water. Second dilutesaline water for desalination is thermally connected with another sideof the high-temperature heat source. Water vapor which has beenevaporated therefrom travels to the refrigeration source, and iscondensed. Hereinafter, a region where water vapor is condensed isreferred to as a water vapor condensation region. The water vaportravels through one-directional diffusion in this embodiment.

An amount of the above-mentioned traveling water vapor from the firstdilute saline water to the concentrated saline water and an amount ofthe traveling water from the second dilute saline water to therefrigeration source increase with the decrease of the total pressure.Therefore, a heat-flow originated in the evaporation and condensationincreases. Further, the amount of the traveling water vapor increaseswhen partial pressure of water vapor is large or the temperature ishigh. Therefore, a throughput of water produced per unit area per unittime increases. Furthermore, the amount of the traveling water vapor islarge when a path-length of the traveling water vapor is short, and islarge when the differential concentration of salt between theconcentrated saline water and the first dilute saline water is large. Inaddition, a region of operation-temperature of the absorptionrefrigerator of this example according to the embodiment is not beyondthe boiling point of the saline water, and is preferably not beyond aboiling point of fresh water. More preferably, a suitable temperaturemay be set according to the above-mentioned reasons. Note that theseboiling points vary with the variation of total pressure and variationof salt concentration.

According to the above-mentioned principles of operation, appropriatemeans for enhancing operations of the apparatus may further be provided.For example, (1) plural gap-members for preventing contact of theconcentrated saline water with the first dilute saline water or forpreventing contact of the fresh water with the second dilute salinewater, when a gap where the water vapor diffuses through one-directionaldiffusion is set short, (2) a vacuum system for establishing the samevacuum state in a space where the plural absorption refrigerator arearranged, (3) means for heating which enable an operation at a hightemperature, (4) means for collecting condensed fresh water properly,and so forth may further be provided. When the fresh water holdingmember for introducing condensed water is brought into close contactwith the surface of condensation of fresh water, growth of large dropsof fresh water is prevented, which is effective in preventing thecontact with the second dilute saline water.

Further, attachments for properly operating the above-mentionedoperations are attached, if necessary, in order to meet the operationalconditions, apparatus configuration, and the environments. For example,an outer wall or a container (not shown) may further be provided toestablish airtightness against the outside and to make a structure suchthat water vapor is not scattered toward the outside by a strong wind orthe like. Furthermore, a side-wall or the like may further be provided,if necessary, which divides a gap of each absorption refrigerator 10from a gap between the fresh water condensing region and the seconddilute water, and which prevents diffusion of water vapor from passingthrough a side of the gap to the other gaps. In addition, a salineconcentration sensor, a thermometer, a vacuum gauge, a water-flowcontroller, a gap-sensor, a fixing member or jig for each member, a gapregulating member, a gap-length varying mechanism, a vacuum pump, avacuum chamber, a water processing apparatus, a sterilizing means, andso forth may further be provided, which are the attached means forpreferably realizing this embodiment.

In connection with the above-mentioned supplying/draining of the salinewater, a water-container, a tube, a watercourse, an appended watercoursemade of a permeating member, a watercourse based on difference betweensurface tension, dropping means, and so forth are further provided, andare optionally miniaturized or configured so as to have a properconfiguration thereof. The means for supplying/exhausting water aredesigned so that distribution of differential concentration in a regionwhere the concentrated saline water and the first dilute saline waterare facing each other and that distribution of concentration of thesecond saline water becomes proper.

When the concentrated saline water is re-evaporated in asalt-precipitation field, which will be described later, theconcentrated saline water is preferably configured so as not to be mixedwith the dilute saline water during draining. The fresh water isexhausted so as not to be contaminated with salt. However, in somecases, a small amount of a saline element may be added thereto.

As a material of the high-temperature heat source plate 111 and therefrigeration source plate 121, plastics, a metal, a composite materialof paper and plastics, and so forth may be employed. Known material suchas sponge made of hydrophilic material, woven cloth, non-woven cloth,paper, or the like, which permeates saline water, may be employed. Inaddition, it may be a coating material including a hydrophilic groupwith which a plate is coated. A piece of sponge of cellulose or thelike, a sheet of woven cloth, a sheet of non-woven cloth, a sheet ofpaper, and so forth may be glued to the plate. Alternatively, in view offacilitating recycling and maintenance, it may be brought into closecontact with the plate using an attachment member for facilitatingseparation thereof from the plate. There are some cases in whichpermeation-state varies slightly because of difference in surfacetension between the concentrated saline water and the first dilutesaline water. Further, respective surfaces of the high-temperature heatsource plate and the refrigeration source plate are disposed normal tothe horizontal plane.

Alternatively, they may be disposed obliquely or horizontally. Further,a portion of the known material which permeates the above-mentionedsaline water may be substituted to a bare saline water-surface.

The high-temperature heat source plate 111, the refrigeration sourceplate 121, the first dilute saline water holding member 122, theconcentrated saline water holding member 112, and the second dilutesaline water holding member 113 are preferred so that respectivethicknesses thereof are thin, from a point of view in maintaining a goodthermal conductive relationship. Further, a large output of theabsorption refrigerator 10 is obtained when the gap is short. Thislength is adjusted to have a prescribed value. Needless to say, thegap-length is optional, provided that mixing of the concentrated salinewater with the first dilute saline water does not take place. However,it is preferred so as to be no more than 10 mm when it is employed in anatmospheric pressure. As an option of the present invention, a thicknessof 0.3 mm for the high-temperature heat source plate, a thickness of 0.3mm for the refrigeration source plate, a thickness of 0.3 mm for thefirst dilute saline water holding member, a thickness of 0.3 mm for thesecond dilute saline water holding member, a thickness of 0.3 mm for theconcentrated saline water holding member, a gap-length of 3 mm of thefacing-region between the concentrated saline water holding member andthe first dilute saline water holding member, and a gap-length of 3 mmof the facing-region between the second dilute saline water holdingmember and the refrigeration source plate may be selected. Note that thevalues regarding these thicknesses are described for the purpose ofillustration and not for limiting.

In case of a gap having an extremely short length, from a point of viewin keeping precisely a length of the gap and preventing contact of theconcentrated saline water with the first saline water, the gap keepingmembers may exist in the gap. The material or the shape thereof isselected so that a saline element or solution does not move via the gapkeeping members. Such gap keeping members may also be employed foradjusting the gap between the second dilute saline water and thecondensation-surface. The gap keeping members, which prevent mixing ofthe concentrated saline water with the first dilute saline water ormixing of the second dilute saline water with the fresh water, areeffective in increasing a throughput per unit area and miniaturizing theapparatus. The gap keeping members are disposed at a prescribedinterval. When the gap is short, when rigidity of the plate isinsufficient, or when shape of the plate is deformed with time, the gapmembers are disposed densely.

Further, as a form of heating the apparatus according to this exampleaccording to the embodiment, the end of the refrigeration sources may beirradiated with solar radiation. The end of the high-temperature heatsources may disperse heat through evaporation of the second dilutesaline water. Alternatively, the heating may be from the side. Further,an insulating material or the like may be employed. In this case, thedesalinating apparatus may be disposed in a container made of atransparent insulating material such as double-layered glass, and may beheated by a solar light. A hothouse may also be employed.

Further, in order to utilizing heat efficiently, a heat-exchanger mayfurther be provided, which heats the first dilute saline water, theconcentrated saline water, and the second dilute saline waterintroduced, utilizing thermal energy of the first dilute saline water,the second dilute saline water, the concentrated saline water exhaustedand the fresh water. Heat is interchanged between the introduced matterand the exhausted matter via a high conductive member of theheat-exchanger so that a temperature of the exhausted matter approachesthat of the introduced matter. Namely, saving energy is achieved,because the first dilute saline water, the second dilute saline water,and the concentrated saline water introduced are heated utilizing heatof the first dilute saline water, the second dilute saline water, theconcentrated saline water exhausted, and the fresh water collected.

Alternatively, when the desalinating apparatus is disposed in a vacuumchamber having a degree of vacuum, a diffusion coefficient of watervapor increases, and a high throughput is also obtained even if theoperation temperature is set at a room-temperature. Evacuation may bedone using a vacuum pump, or a Torricelli's vacuum may be employed. Thepressure is in a region not below a saturated pressure of the water atthe operation temperature. Namely, the pressure in the vacuum chamber,in this case, is kept in a region where the first dilute saline waterdoes not boil. When the gap is short, the operation may be done in avacuum state in which some residual air molecules remain. The vacuumchamber is a airtight chamber of stainless steel, plastics, aluminum, orthe like, which has a durable rigidity against differential pressureagainst the atmospheric pressure, or a non-airtight rigid chamber of areinforced concrete covered with an airtight soft member of plastic filmof polyethylene or the like, for example. In this case, it may befloated on water, or be disposed in water, in order to prevent a damageof the covering member. Alternatively, an airtight basement may beemployed as the vacuum chamber.

In the above-mentioned example according to the embodiment, the pluralabsorption refrigerators 10 having plainer configuration are alignedalong a straight line. However, there is also an example according to anembodiment in which they are aligned along a closed line. Namely, anumber of absorption refrigerators 10, for example, a number of10-100000, each having the structure shown in FIG. 2, are alignedserially along a closed polygon, a circle, or an ellipse so that nospecial end exists and that any high-temperature heat source is disposednext to the adjacent refrigeration source. Shape of the alignment mayoptionally be adjusted by inserting a high conductive member into thealignment. Accordingly, the heat flows along a closed eddy line.

Although the absorption refrigerator 10 which is employed in the exampleaccording to the embodiment is an open regeneration type, any heatsource may be employed for regenerating the concentrated saline water.In particular, a salt-precipitation field in an arid region is suitablebecause of utilization of solar thermal energy or dry air. Thesalt-precipitation field is a heat source which is remarkably easy inmaintenance and which is hardly caused to have bad influence of a strongwind or a cloud of dust.

Because precipitation is extremely little in arid regions, seawater iseasily condensed when stored on soil having no water-permeability, andthe costs of heat source are extremely low. When supplementary solidsalt stored in the salt precipitation field is utilized for preventingdecrease of salt-concentration, fluctuation of salt-concentration of theconcentrated saline water due to weather conditions can be suppressed,without influence due to precipitation or exceptional lack of sunshine.A water treatment and a water quality management such as prevention oforganic matters, fungi, miscellaneous bacteria, etc. is optionally done.

FIG.1 corresponds to single-effect distillation. When multi-effectdistillation is to be done, plural appended plates, each having a seconddilute saline water holding member which is brought into close contacttherewith, are employed. Further, when the above-mentioned alignment ofplural absorption refrigerators is defined as one unit, the plural unitsmay be disposed in one desalinating apparatus.

As another embodiment of the present invention, a desalination system isprovided, which includes means for supplying first dilute saline water,means for supplying concentrated saline water, means for supplyingsecond dilute saline water for desalination, an absorption refrigeratorwhich employs the concentrated saline water and the first dilute salinewater, means for evaporating the second dilute saline water using heatwhich flow out from a high-temperature heat source of the absorptionrefrigerator, means for collecting condensed fresh water, whichcondenses water vapor evaporated from the second dilute saline waterusing heat which flows in a refrigeration source of the absorptionrefrigerator.

As appended means, means for heating the concentrated saline water andmeans for heating dilute saline water may further be provided. In thiscase, means for exchanging heat between water which flows in theabsorption refrigerator and water which flows out therefrom may furtherbe provided. Alternatively, a vacuum system may further be provided,which evacuates the absorption refrigerator.

Operation as a desalination system utilizing renewable natural energy isachieved, for example, when a salt-precipitation field is furtherprovided, which re-concentrate the concentrated saline water in whichsalt-concentration has decreased.

As an example according to an embodiment, there is a seawaterdesalinating system, wherein an infrastructure is provided for eachurban house, which is composed of a seawater supply system as means forsupplying seawater that can be employed as both of means for supplying afirst dilute saline water and means for supplying second dilute salinewater, and a concentrated saline water supply/drainage as means forsupplying concentrated saline water, wherein the above desalinatingapparatus system is provided in each house. In this case, thedesalinating apparatus is expected to have the volume corresponding tothe household refrigerator. Because fresh water produced is distilledwater, it is clean. Mineral elements may be added thereto, if necessary.

An embodiment of a desalination system according to the presentinvention is not limited to this example. For example, as anotherexample according to an embodiment, there is a desalination system inwhich desalination is done collectively in a suburban salt-precipitationfield.

As still another embodiment of the present invention, an example of adesalinating method according to the present invention is explainedabout the operation of the above-mentioned desalinating apparatus,referring to FIG. 1 and FIG. 2.

According to a step of supplying first dilute saline water to arefrigeration source of an absorption refrigerator, the first salinewater is supplied to a first dilute saline water holding member 122.According to a step of supplying concentrated saline water having ahigher molar salt-concentration than that of the first dilute salinewater to a high-temperature heat source of the absorption refrigerator,the concentrated saline water is supplied to a concentrated saline waterholding member 112. Water vapor evaporated from the first dilute salinewater diffuses through a gap, and is absorbed in a surface of theconcentrated saline water holding member 112. Through this evaporation,evaporative latent heat is taken from the refrigeration source 12 , andthe latent heat by absorption is released for the high-temperature heatsource, thereby an operation as an absorption refrigerator is achieved.A second dilute saline water holding member 113 is brought into closecontact with another surface of a high-temperature heat source plate111, which is on the reverse side for the concentrated saline waterholding member 112. According to a step of supplying second dilutesaline water for desalination to the absorption refrigerator, the seconddilute saline water for desalination is supplied to the second dilutewater holding member 113. Because the second dilute saline water holdingmember 113 and the concentrated saline water holding member 112 areseparate from each other, mixing due to contact of the concentratedsaline water with the second dilute saline water does not take place.Fresh water condenses on a surface of a refrigeration source plate 121,which is on the reverse side for first dilute saline water holdingmember 122. The concentrated saline water supplied from the top descendsby gravity, which is exhausted according to a step of draining theconcentrated saline water in which salt-concentration has decreased dueto absorption of water. Also, the first dilute saline water and thesecond dilute saline water supplied from the top descends by gravity,respectively, and are exhausted according to a step of draining thefirst dilute saline water in which salt-concentration has increased dueto evaporation of water, and a step of draining the second dilute salinewater in which salt-concentration has increased due to evaporation ofwater. The fresh water is collected according to a step of collectingthe fresh water condensed.

As a kind of salt which is employed for this absorption refrigerator,known salt having water-solubility such as sodium chloride, calciumchloride, potassium chloride, magnesium chloride, zinc nitrate, ammoniumsulfate, lithium bromide, sodium bromide, etc., and mixture thereof maybe employed. Also, concentrated seawater may be employed. The firstdilute saline water is a saline water having a lower molarsalt-concentration than that of the concentrated saline water. Seawateror saline groundwater may be employed. Difference of molar elevation ofboiling points between the concentrated saline water and the firstdilute saline water is in a range so that it sufficiently exceeds thevalue of molar elevation of boiling point of the second dilute salinewater. Namely, the necessary condition for desalination using thesingle-effect absorption refrigerator is that temperature differencegenerated by the absorption refrigerator sufficiently exceeds the valueof molar elevation of boiling point of the second dilute saline waterfor desalination. Specifically, the first dilute saline water and thesecond dilute saline water may be the same kind of saline water.Further, a multi-effect absorption refrigerator may be employed.

Hereinafter, as an example of an operation for facilitating explanation,a method of producing fresh water according to the embodiment isexplained assuming that concentrated seawater is employed as theconcentrated saline water, and that seawater is employed as the firstdilute saline water and the second dilute saline water. This example isnot limiting utilization of any kinds of saline water, as mentionedabove.

In this case, an initial concentration of the concentrated sea water isapproximately equal to or more than 10%, preferably equal to or morethan 15%. An initial concentration of the first dilute saline water andthe second dilute saline water is about 3.5%. Supply and exhaustion aredone to achieve a range of a salt-concentration such that temperaturedifference between the second dilute saline water holding member 113 andthe refrigeration source plate 121 becomes sufficiently larger thanmolar elevation of boiling point of the second dilute saline water ineach facing region, using means for supplying/draining the first dilutesaline water, means for supplying/draining the second dilute salinewater, means for supplying/draining the concentrated saline water, whichmeans are not shown. Supply/exhaustion of respective kinds of salinewater and collection of the fresh water are appropriately done using atube, a watercourse, a watercourse made of an appended permeatingmember, a dropping member, a valve, and so forth. Therefore, diffusingwater vapor evaporated from the second dilute saline water reaches tothe refrigeration source plate 121, and condensed water is generated onthe surface of the fresh water condensing region.

In the first dilute saline water and the second dilute saline water, thesalt-concentrations increase with evaporation of water thereof, and arekept at an appropriate concentration defined by the quality of water sothat a problem of precipitation of scale such as calcium sulfate doesnot arise. Further, with the absorption of water vapor into theconcentrated saline water, the concentration of the concentrated salinewater is decreased. The temperature difference between thehigh-temperature heat source and the refrigeration source of theabove-mentioned absorption refrigerator becomes large when thedifference of salt-concentration is large. Management of concentrationsis important in supplying/draining these kinds of saline water, in orderto obtain a prescribed temperature difference for the concentration ofthe second dilute saline water in a wide range of concentration.

When decrease in salt-concentration of the concentrated saline waterwhich has been once drained is relatively small, a combination of thedrained concentrated saline water and the first dilute saline waterhaving an initial concentration may be re-supplied to the absorptionrefrigerator. Similarly, when increment of the salt-concentration of thefirst dilute saline water once drained is relatively small, acombination of the first dilute saline water once drained and theconcentrated saline water having an initial concentration may bere-supplied to the absorption refrigerator.

A throughput of this example per unit area of the fresh water condensingregion is from several to several 100 kg/day. When the gap-length isshort, a throughput per unit volume of the apparatus of from several 10to 100000 kg/day is obtained. Therefore, a small apparatus can achieve alarge throughput, and maintenance such as wind-breaking is extremelyfacilitated.

In the above, when the inside of the absorption refrigerator and a spacebetween the second saline water and the condensing region where thewater vapor evaporated from the second dilute saline water condenses isset to have substantially the same pressure, these regions can beevacuated using a single vacuum chamber. Therefore, maintenance of thevacuum system, which requires no complicated vacuum sealing member, isfacilitated even if many absorption refrigerators are employed. Thevacuum state improves the diffusion coefficient greatly, and improvesthe throughput per unit time.

Heating of the apparatus or heating of the first dilute saline water,the second dilute saline water, and the concentrated saline water to beintroduced is effective in improving throughput under operation atatmospheric pressure. Solar thermal energy or waste heat is utilized forthe heating. However, a boiler or electric heating which consumes fossilfuel or electricity may be employed. The kind of salt may be optionallyselected, in view of heat of mixing, so that heat of mixing is generatedsubstantially during processes of evaporation/condensing accompanied bydilution of the concentrated saline water and condensation of the firstdilute saline water.

In the above, partial pressure of water vapor is increased according toincrease of operation temperature of the absorption refrigerator, whichachieves increment of throughput according to increase of an amount ofdiffusion. The increase in temperature is in a range not greater thanthe boiling point. Even when the vacuum is employed, a slight heating isoccasionally effective. In other words, in one mode of operation, heatin the desalinating apparatus is taken out slightly by evacuation ofwater vapor by the vacuum pump. The heating works for compensating this.

As described above, the present invention achieves fresh water supplyusing natural energy, and simultaneously provides a novel method ofproducing a right of emitting carbon dioxide. Namely, when an existingdesalinating method is substituted to the method of producing freshwater according to the present invention, a right of emitting carbondioxide is produced according to reduction of carbon dioxide emission.Further, when vegetation is grew as means for fixing carbon dioxide inthe atmosphere, a right of producing carbon dioxide is producedaccording to the reduction of carbon dioxide emission corresponding toan amount of photosynthesis in the vegetation.

The present invention disclosed herein provides a novel desalinatingapparatus, a desalination system, a method of desalinating saline water,and a method of producing right of carbon dioxide, wherein in view ofthe teachings disclosed in the above-mentioned detailed explanation, apractice of the present invention is not limited to the above-mentionedexamples for explaining the preferred embodiments of the presentinvention, and wherein the present invention may be practiced as otherembodiments with variations within the scope of the claims as follows ormay be practiced without supplementary forms or elements which areappended for explaining the preferred embodiments.

Industrial Applicability

With the operation of the absorption refrigerator using concentratedsaline water and dilute saline water, the desalinating apparatusaccording to the present invention provides water for household use,agricultural use, and industrial use in an arid region, a region havingproblems related to salt precipitation, a region where fresh water isshort, or a region where severe water-pollution due to a nonvolatilehazardous material exists. The desalination system according to thepresent invention achieves desalination using natural energy. Further, abusiness is enabled for preserving global environment, which isaccompanied by reduction of carbon dioxide emission or fixing of carbondioxide in the atmosphere, in connection with global environmentalissues. Further, it contributes to improvement of soil in a region whereproblems related to salt-precipitation take place or to prevention ofproblems related to salt-precipitation which is accompanied by variationof underground water level.

What is claimed is:
 1. A desalinating apparatus, comprising a pluralityof absorption refrigerator units, each including: a refrigeration sourceplate having no water-permeability; a first dilute saline water holdingmember which is brought into close contact with a surface of therefrigeration source plate; a high-temperature heat source plate havingno water-permeability; a concentrated saline water holding member whichis brought into close contact with a surface of the high-temperatureheat source plate, and which is disposed opposite the first dilutesaline water holding member; and a second dilute saline water holdingmember which is brought into close contact with another surface of thehigh-temperature heat source plate, wherein the plurality of absorptionrefrigerator units are aligned in series in a serial arrangement, andwherein each of the second dilute saline water holding member in theserial arrangement is disposed opposite another surface of the adjacentrefrigeration source plate.
 2. The desalinating apparatus according toclaim 1, wherein the serial arrangement is made along a closed line. 3.A method of desalinating saline water using an absorption refrigerator,comprising the steps of: supplying a first dilute saline water to arefrigeration source of the absorption refrigerator; supplying aconcentrated saline water having a higher molar elevation of boilingpoint than that of the first dilute saline water to a high-temperatureheat source of the absorption refrigerator; supplying a second dilutesaline water for desalination to the absorption refrigerator; drainingthe first dilute saline water in which a salt-concentration thereof hasbeen increased due to an evaporation of water; draining the concentratedsaline water in which a salt-concentration thereof has been decreaseddue to an absorption of water; draining the second dilute saline waterin which a salt-concentration thereof has been increased due to anevaporation of water; and collecting a condensed fresh water, whereinthe second dilute saline water is evaporated utilizing a heat whichflows out from the high-temperature heat source of the absorptionrefrigerator, and wherein the water vapor which has evaporated from thesecond dilute saline water is condensed utilizing a heat which isabsorbed in the absorption refrigerator, thereby obtaining the condensedfresh water.
 4. The method of desalinating saline water according toclaim 3, further comprising the step of heating the first dilute salinewater, the second dilute saline water, and the concentrated saline watersupplied.
 5. A desalinating apparatus comprising: an absorptionrefrigerator including a high-temperature heat source and arefrigeration source, which utilizes a concentrated saline water and afirst dilute saline water; means for supplying the first dilute salinewater to the absorption refrigerator, the first dilute saline waterbeing drained from the absorption refrigerator when a salt-concentrationthereof has been increased; means for supplying the concentrated salinewater to the absorption refrigerator, the concentrated saline waterbeing drained from the absorption refrigerator when a salt-concentrationthereof has been decreased; and means for generating a water vapor froma second dilute saline water supplied for desalination, utilizing a heatwhich flows out from the high-temperature heat source, the second dilutesaline water being drained from the absorption refrigerator when asalt-concentration thereof has been increased; wherein the water vaporgenerated from the second dilute saline water is condensed utilizing theheat which is absorbed in the refrigeration source.
 6. A desalinatingapparatus comprising: a plurality of absorption refrigerators utilizinga concentrated saline water and a first dilute saline water, eachabsorption refrigerator including a high-temperature heat source and arefrigeration source; means for supplying the first dilute saline waterto each absorption refrigerator, the first dilute saline water beingdrained from the absorption refrigerator when a salt-concentrationthereof has been increased; means for supplying the concentrated salinewater to each absorption refrigerator, the concentrated saline waterbeing drained from the absorption refrigerator when a salt-concentrationthereof has been decreased; and means for generating a water vapor froma second dilute saline water supplied for desalination, utilizing a heatwhich flows out from the high-temperature heat source of each absorptionrefrigerator, the second dilute saline water being drained from theabsorption refrigerator when a salt-concentration thereof has beenincreased; wherein the plurality of absorption refrigerators are alignedin series in a serial arrangement so that the water vapor generated fromthe second dilute saline water of the high-temperature heat source ofeach absorption refrigerator is condensed utilizing the heat which isabsorbed in the refrigeration source of the adjacent absorptionrefrigerator in the serial arrangement.